1. Field of the Invention
The present invention relates to a high-frequency module.
2. Description of the Related Art
An in-vehicle radar device to be mounted on an automobile uses a high-frequency module which is operated in a millimeter wave range. The in-vehicle radar is widespread for the purpose of measuring a distance to an automobile which is running ahead, for instance. An example of the in-vehicle radar device is disclosed in Patent Literature 1.
In the Patent Literature 1, an active element such as a monolithic microwave integrated circuit (MMIC) is mounted on one surface of a metal substrate via a circuit substrate, and an antenna for transmitting and receiving a high-frequency signal is provided on the other surface of the metal substrate. In this structure, it is necessary to form a hole in the metal substrate so as to constitute a waveguide tube for guiding the high-frequency signal from the antenna to the active element. According to the Patent Literature 1, manufacturing time for the high-frequency module is reduced by forming the hole as the waveguide tube on the metal substrate while the circuit substrate is attached to the metal substrate.
Meanwhile, Patent Literature 2 discloses an FM radar module configured to connect an MMIC to an antenna so as to carry a high frequency by use of a pin.
However, forming the hole in the metal substrate requires a high cost. Accordingly, formation of the through hole serving as the waveguide tube in the metal substrate as disclosed in Patent Literature 1 incurs an increase in manufacturing costs of the high-frequency module.
(Patent Literature 1) Japanese Unexamined Patent Publication No. 2003-86728
(Patent Literature 2) Japanese Unexamined Patent Publication No. 8(1996)-114667